using System;
using System.Collections.Concurrent;
using System.Numerics;
using System.Threading;
using AcDream.Core.Physics;
using DatReaderWriter.Types;

namespace AcDream.Core.Vfx;

/// <summary>
/// <see cref="IAnimationHookSink"/> that translates particle-bearing
/// animation hooks into <see cref="ParticleSystem"/> spawn / stop calls.
///
/// <para>
/// Hook types handled (r04 §6):
/// <list type="bullet">
///   <item><description>
///     <see cref="CreateParticleHook"/> — spawn an emitter from the
///     hook's <c>EmitterInfoId</c> at the entity's world pose plus the
///     hook offset. Retail attaches to a specific mesh part; we
///     attach to the entity's root and will refine per-part when the
///     renderer exposes per-part world transforms.
///   </description></item>
///   <item><description>
///     <see cref="CreateBlockingParticleHook"/> — same as
///     CreateParticleHook but the retail sequencer blocks animation
///     progression until the particle is done. We spawn the emitter
///     identically; the "blocking" semantics belong to the sequencer.
///   </description></item>
///   <item><description>
///     <see cref="DestroyParticleHook"/> — stop the most-recent emitter
///     matching the hook's <c>EmitterId</c>. Deferred to a future pass
///     when we retain per-entity emitter-id → handle maps.
///   </description></item>
///   <item><description>
///     <see cref="StopParticleHook"/> — pause all emitters on the
///     entity (fade out).
///   </description></item>
///   <item><description>
///     <see cref="DefaultScriptHook"/> / <see cref="DefaultScriptPartHook"/>
///     — trigger the entity's <c>DefaultScriptId</c> PhysicsScript.
///     Requires PhysicsScript table; deferred.
///   </description></item>
///   <item><description>
///     <see cref="CallPESHook"/> — fire a PhysicsScript by id.
///     Deferred until DRW exposes PhysicsScript dat.
///   </description></item>
/// </list>
/// </para>
///
/// <para>
/// Per-entity emitter handle tracking is kept here so DestroyParticle /
/// StopParticle can target the right emitter when a server-sent
/// <c>PlayEffect</c> fires.
/// </para>
/// </summary>
public sealed class ParticleHookSink : IAnimationHookSink
{
    private readonly ParticleSystem _system;

    // entityId → most-recently-spawned emitter handle per emitterId.
    // DestroyParticleHook.EmitterId is effectively an application-layer
    // key ("the smoke trail I spawned 2 seconds ago"), so we track by
    // (entity, emitterId).
    private readonly ConcurrentDictionary<(uint EntityId, uint EmitterId), int> _handlesByKey = new();
    // entityId → set of live emitter handles. Dictionary-as-set so we can
    // remove individual handles when their emitter dies (M4 fix —
    // ConcurrentBag couldn't drop entries, so handles for naturally-expired
    // emitters used to leak).
    private readonly ConcurrentDictionary<uint, ConcurrentDictionary<int, byte>> _handlesByEntity = new();
    // Reverse lookup: handle → (entity, key) for O(1) cleanup on EmitterDied.
    private readonly ConcurrentDictionary<int, (uint EntityId, uint KeyId)> _trackingByHandle = new();
    private readonly ConcurrentDictionary<uint, ParticleRenderPass> _renderPassByEntity = new();
    private readonly ConcurrentDictionary<uint, Quaternion> _rotationByEntity = new();
    // C.1.5b #56: per-entity static part transforms (PlacementFrames[Resting]
    // baked into a Matrix4x4 per Setup part). When set, SpawnFromHook applies
    // partTransforms[hook.PartIndex] to the hook offset BEFORE rotating to
    // world space. Without this, every emitter in a multi-part Setup
    // collapses to the entity root (the bug). Cleared by StopAllForEntity.
    // For ANIMATED entities this map would need a per-tick refresh similar
    // to UpdateEntityAnchor — deferred to a future phase.
    private readonly ConcurrentDictionary<uint, IReadOnlyList<Matrix4x4>> _partTransformsByEntity = new();
    private int _anonymousEmitterSerial;

    public ParticleHookSink(ParticleSystem system)
    {
        _system = system ?? throw new ArgumentNullException(nameof(system));
        _system.EmitterDied += OnEmitterDied;
    }

    private void OnEmitterDied(int handle)
    {
        if (!_trackingByHandle.TryRemove(handle, out var t))
            return;
        _handlesByKey.TryRemove((t.EntityId, t.KeyId), out _);
        if (_handlesByEntity.TryGetValue(t.EntityId, out var bag))
            bag.TryRemove(handle, out _);
    }

    public void OnHook(uint entityId, Vector3 entityWorldPosition, AnimationHook hook)
    {
        switch (hook)
        {
            case CreateParticleHook cph:
                SpawnFromHook(entityId, entityWorldPosition,
                    emitterInfoId: (uint)cph.EmitterInfoId,
                    offset:        cph.Offset.Origin,
                    partIndex:     (int)cph.PartIndex,
                    logicalId:     cph.EmitterId);
                break;

            case CreateBlockingParticleHook:
                // Retail's CreateBlockingParticleHook is a sentinel (no
                // payload) — the sequencer pauses advancement until the
                // current particle emitter finishes. We surface this as
                // "no spawn needed, just keep the current particle alive";
                // blocking semantics live in the sequencer, not here.
                break;

            case DestroyParticleHook dph:
                if (_handlesByKey.TryRemove((entityId, dph.EmitterId), out var handleToDestroy))
                    _system.StopEmitter(handleToDestroy, fadeOut: false);
                break;

            case StopParticleHook sph:
                if (_handlesByKey.TryGetValue((entityId, sph.EmitterId), out var handleToStop))
                    _system.StopEmitter(handleToStop, fadeOut: true);
                break;

            // DefaultScript / CallPES are wired when PhysicsScript loading
            // is available. They arrive at the sink but we can't act until
            // the script table returns a real emitter list.
        }
    }

    public void SetEntityRenderPass(uint entityId, ParticleRenderPass renderPass)
        => _renderPassByEntity[entityId] = renderPass;

    public void SetEntityRotation(uint entityId, Quaternion rotation)
        => _rotationByEntity[entityId] = rotation;

    /// <summary>
    /// Register per-part static transforms for an entity. The caller
    /// (typically <c>EntityScriptActivator</c>) precomputes one
    /// <see cref="Matrix4x4"/> per Setup part using
    /// <c>SetupPartTransforms.Compute</c> and pushes them here at spawn
    /// time. <see cref="SpawnFromHook"/> applies
    /// <c>partTransforms[hook.PartIndex]</c> to the hook offset BEFORE
    /// transforming to world space. Cleared on
    /// <see cref="StopAllForEntity"/>.
    /// </summary>
    public void SetEntityPartTransforms(uint entityId, IReadOnlyList<Matrix4x4> partTransforms)
        => _partTransformsByEntity[entityId] = partTransforms;

    public void ClearEntityRenderPass(uint entityId)
        => _renderPassByEntity.TryRemove(entityId, out _);

    /// <summary>
    /// Refresh every live emitter on this entity to a new world anchor +
    /// rotation. The owning subsystem (sky-PES driver, animation tick)
    /// drives this each frame for AttachLocal emitters so they track their
    /// moving parent — retail-faithful via
    /// <c>ParticleEmitter::UpdateParticles</c> at <c>0x0051d2d4</c>, which
    /// re-reads the parent frame each tick when <c>is_parent_local != 0</c>.
    /// Safe to call for entities with no live emitters (no-op).
    /// </summary>
    public void UpdateEntityAnchor(uint entityId, Vector3 anchor, Quaternion rotation)
    {
        _rotationByEntity[entityId] = rotation;
        if (!_handlesByEntity.TryGetValue(entityId, out var bag))
            return;
        foreach (var handle in bag.Keys)
            _system.UpdateEmitterAnchor(handle, anchor, rotation);
    }

    public void StopAllForEntity(uint entityId, bool fadeOut)
    {
        if (_handlesByEntity.TryRemove(entityId, out var handles))
        {
            foreach (var handle in handles.Keys)
            {
                _system.StopEmitter(handle, fadeOut);
                _trackingByHandle.TryRemove(handle, out _);
            }
        }

        foreach (var key in _handlesByKey.Keys)
        {
            if (key.EntityId == entityId)
                _handlesByKey.TryRemove(key, out _);
        }

        ClearEntityRenderPass(entityId);
        _rotationByEntity.TryRemove(entityId, out _);
        _partTransformsByEntity.TryRemove(entityId, out _);
    }

    private void SpawnFromHook(
        uint entityId,
        Vector3 worldPos,
        uint emitterInfoId,
        Vector3 offset,
        int partIndex,
        uint logicalId)
    {
        // Spawn position: entity pose + hook offset, with the hook
        // offset first passed through the per-part transform when
        // available (C.1.5b #56 fix). Without the per-part transform,
        // every emitter in a multi-emitter PES script collapses to the
        // entity root — visible symptom: ground-buried portal swirls.
        var rotation = _rotationByEntity.TryGetValue(entityId, out var rot)
            ? rot
            : Quaternion.Identity;
        Vector3 partLocal = offset;
        if (_partTransformsByEntity.TryGetValue(entityId, out var partTransforms)
            && partIndex >= 0
            && partIndex < partTransforms.Count)
        {
            partLocal = Vector3.Transform(offset, partTransforms[partIndex]);
        }
        var anchor = worldPos + Vector3.Transform(partLocal, rotation);
        var renderPass = _renderPassByEntity.TryGetValue(entityId, out var pass)
            ? pass
            : ParticleRenderPass.Scene;

        int handle = _system.SpawnEmitterById(
            emitterId: emitterInfoId,
            anchor: anchor,
            rot: rotation,
            attachedObjectId: entityId,
            attachedPartIndex: partIndex,
            renderPass: renderPass);

        uint keyId = logicalId != 0
            ? logicalId
            : 0x80000000u | (uint)Interlocked.Increment(ref _anonymousEmitterSerial);
        if (logicalId != 0 && _handlesByKey.TryRemove((entityId, keyId), out var oldHandle))
        {
            _system.StopEmitter(oldHandle, fadeOut: false);
            _trackingByHandle.TryRemove(oldHandle, out _);
        }

        _handlesByKey[(entityId, keyId)] = handle;
        _handlesByEntity
            .GetOrAdd(entityId, _ => new ConcurrentDictionary<int, byte>())
            .TryAdd(handle, 0);
        _trackingByHandle[handle] = (entityId, keyId);
    }
}